diff options
Diffstat (limited to 'brotli/enc/encode.cc')
| -rw-r--r-- | brotli/enc/encode.cc | 72 |
1 files changed, 27 insertions, 45 deletions
diff --git a/brotli/enc/encode.cc b/brotli/enc/encode.cc index 7d54dbe..b492421 100644 --- a/brotli/enc/encode.cc +++ b/brotli/enc/encode.cc @@ -122,18 +122,30 @@ void StoreHuffmanTreeOfHuffmanTreeToBitMask( }; // Throw away trailing zeros: int codes_to_store = kCodeLengthCodes; - for (; codes_to_store > 3; --codes_to_store) { + for (; codes_to_store > 0; --codes_to_store) { if (code_length_bitdepth[kStorageOrder[codes_to_store - 1]] != 0) { break; } } - WriteBits(4, codes_to_store - 3, storage_ix, storage); - const int skip_two_first = - code_length_bitdepth[kStorageOrder[0]] == 0 && - code_length_bitdepth[kStorageOrder[1]] == 0; - WriteBits(1, skip_two_first, storage_ix, storage); - - for (int i = skip_two_first * 2; i < codes_to_store; ++i) { + int num_codes = 0; + for (int i = 0; i < codes_to_store; ++i) { + if (code_length_bitdepth[kStorageOrder[i]] != 0) { + ++num_codes; + } + } + if (num_codes == 1) { + codes_to_store = kCodeLengthCodes; + } + int skip_some = 0; // skips none. + if (code_length_bitdepth[kStorageOrder[0]] == 0 && + code_length_bitdepth[kStorageOrder[1]] == 0) { + skip_some = 2; // skips two. + if (code_length_bitdepth[kStorageOrder[2]] == 0) { + skip_some = 3; // skips three. + } + } + WriteBits(2, skip_some, storage_ix, storage); + for (int i = skip_some; i < codes_to_store; ++i) { uint8_t len[] = { 2, 4, 3, 2, 2, 4 }; uint8_t bits[] = { 0, 5, 1, 3, 2, 13 }; int v = code_length_bitdepth[kStorageOrder[i]]; @@ -174,7 +186,7 @@ void StoreHuffmanCode(const EntropyCode<kSize>& code, int alphabet_size, } if (code.count_ == 0) { // emit minimal tree for empty cases // bits: small tree marker: 1, count-1: 0, max_bits-sized encoding for 0 - WriteBits(3 + max_bits, 0x01, storage_ix, storage); + WriteBits(4 + max_bits, 0x1, storage_ix, storage); return; } if (code.count_ <= 4) { @@ -194,7 +206,7 @@ void StoreHuffmanCode(const EntropyCode<kSize>& code, int alphabet_size, } } // Small tree marker to encode 1-4 symbols. - WriteBits(1, 1, storage_ix, storage); + WriteBits(2, 1, storage_ix, storage); WriteBits(2, code.count_ - 1, storage_ix, storage); for (int i = 0; i < code.count_; ++i) { WriteBits(max_bits, symbols[i], storage_ix, storage); @@ -211,8 +223,6 @@ void StoreHuffmanCode(const EntropyCode<kSize>& code, int alphabet_size, } return; } - WriteBits(1, 0, storage_ix, storage); - uint8_t huffman_tree[kSize]; uint8_t huffman_tree_extra_bits[kSize]; int huffman_tree_size = 0; @@ -229,40 +239,8 @@ void StoreHuffmanCode(const EntropyCode<kSize>& code, int alphabet_size, EntropyCode<kCodeLengthCodes> huffman_tree_entropy; BuildEntropyCode(huffman_tree_histogram, 5, kCodeLengthCodes, &huffman_tree_entropy); - Histogram<kCodeLengthCodes> trimmed_histogram = huffman_tree_histogram; - uint8_t* last_code = &huffman_tree[huffman_tree_size - 1]; - while (*last_code == 0 || *last_code >= 17) { - trimmed_histogram.Remove(*last_code--); - } - int trimmed_size = trimmed_histogram.total_count_; - bool write_length = false; - if (trimmed_size >= 4 && trimmed_size <= 195 && - trimmed_size < huffman_tree_size) { - EntropyCode<kCodeLengthCodes> trimmed_entropy; - BuildEntropyCode(trimmed_histogram, 5, kCodeLengthCodes, &trimmed_entropy); - int huffman_bit_cost = HuffmanTreeBitCost(huffman_tree_histogram, - huffman_tree_entropy); - int trimmed_bit_cost = HuffmanTreeBitCost(trimmed_histogram, - trimmed_entropy);; - trimmed_bit_cost += (trimmed_size < 68 ? 7 : 8); - if (trimmed_bit_cost < huffman_bit_cost) { - write_length = true; - huffman_tree_size = trimmed_size; - huffman_tree_entropy = trimmed_entropy; - } - } - StoreHuffmanTreeOfHuffmanTreeToBitMask( &huffman_tree_entropy.depth_[0], storage_ix, storage); - WriteBits(1, write_length, storage_ix, storage); - if (write_length) { - WriteBits(1, huffman_tree_size >= 68, storage_ix, storage); - if (huffman_tree_size < 68) { - WriteBits(6, huffman_tree_size - 4, storage_ix, storage); - } else { - WriteBits(7, huffman_tree_size - 68, storage_ix, storage); - } - } StoreHuffmanTreeToBitMask(&huffman_tree[0], &huffman_tree_extra_bits[0], huffman_tree_size, huffman_tree_entropy, storage_ix, storage); @@ -322,9 +300,13 @@ void ComputeDistanceShortCodes(std::vector<Command>* cmds, int cur_dist = (*cmds)[i].copy_distance_; if (cur_dist == 0) break; int dist_code = cur_dist + 16; + int limits[16] = { 0, 4, 10, 11, + 6, 6, 11, 11, + 11, 11, 11, 11, + 12, 12, 12, 12 }; for (int k = 0; k < 16; ++k) { // Only accept more popular choices. - if (cur_dist < 11 && ((k >= 2 && k < 4) || k >= 6)) { + if (cur_dist < limits[k]) { // Typically unpopular ranges, don't replace a short distance // with them. continue; |